Electromagnetic radiation (EMR) absorbing materials are used for many different purposes. They can be used to create anechoic chambers, to reduce spurious signals near airport radar installations, to shield electronic components from electromagnetic interference (EMI), to prevent the escape of radiation from radiation-producing devices, such as a microwave oven, as well as many other uses.
EMR-absorbing materials are made in many different ways. One way is to use a block of foam with carbon particles dispersed within the foam. Composite laminates are sometimes made so that they absorb EMR. One type of conductive composite laminate uses a fabric having conductive fibers woven into the fabric. See U.S. Pat. No. 5,102,727 to Pittman. Conductive fabrics can also be used in making honeycomb and other open-celled materials; these are especially useful in applications where high strength-to-weight ratios are needed.
While the Pittman patent shows a method for obtaining multi-directional conductivity within a fabric, it has its drawbacks. Weaving conductive yarns in the fill or weft direction is highly flexible since, for example, non-conductive weft fibers can easily be replaced by conductive weft fibers during the weaving operation. Changing warp or web fibers during a weaving operation is, however, laborious and expensive.